Lutman—Life History and Cytology of the Smuts. 1197 
Dangeard and Sappin-Trouffy regarded the fusion of nuclei in 
the teleutospore as the sexual process in the rusts and paid little 
attention to the origin of the binucleated condition further than 
to discover that there were pairs of nuclei of different origin far 
back in the mycelium. 
Maire (28) was able to show that the vegetative cells of the 
hyphae of Endophyllum are uninucleated up to the base of the 
aecidium. This condition was considered general by him for 
the aecidium bearing mycelium. The end cells are binucleated 
and from these binucleated end cells the spores are produced. 
To Maire is due the credit of recognizing the general signify 
cance of this discovery in his suggestion of the alternation of 
generations in the rusts. The change from sporophvte to game- 
tophyte takes place in the reduction divisions to form the four 
promycelial cell nuclei. 
Holden and Harper (24) showed that the nuclear divisions in 
the promycelium of Coleosporium sonchi-arvensis are of the or¬ 
dinary mitotic type with from six to ten chromosomes present 
instead of two as had been claimed by Maire. 
When the origin of the sporophyte had been pointed out by 
Maire as lying at the beginning of the binucleated condition in¬ 
stead of in the fusion of the two nuclei in the teleutospore, as 
Dangeard had suggested, the importance of finding the first cells 
having the two nuclei and the method of their origin was much 
increased. 
Blackman (2) in 1904 and Christman (7) in 1905 found the 
origin of the binucleated condition in rusts with aecidia of the 
caeoma type. Blackman in Phragmidium violaceum discovered 
that the binucleated condition arises by the entrance of the nu¬ 
cleus of a vegetative cell into a large cell, the so-called basidum, 
above it. Christman in Phragmidium speciosum found a 
fusion of two such cells giving rise to a binucleated cell from 
which arises the row of two nucleated aecidiospores. 
Blackman and Fraser (3) found in the aecidia of Hromyces 
poae and Puccinia poarmn that the fusion was of the type pre¬ 
viously described by Blackman, while in Melampsora Bostrupi 
there were evidences of a fusion like those described by Christ¬ 
man in Phrag. speciosum. Christman (8) later described 
